The popular constitutive formulations of rate-and-state friction offer two end member views on whether friction evolves only with slip (Slip law) or with time even without slip (Aging law). While rate stepping experiments show support for the Slip law, laboratory observed frictional behavior near zero slip rates has traditionally been inferred as supporting Aging law style time-dependent healing, in particular from the slide-hold-slide experiments of [?BeelerTW94a].
